site type not specified, may be >>Al-OH or >>Si-OH;calculated value of logK: dependence of the free energy of sorption on ion solvation manifested by a linear dependence on the inverse of the dielectric constant; emphasizes that logK, thought to be characteristic of both the sorbing ion and the solid, should by replaced by a more fundamental ion intrinsic constant independent of the solid, once solvation effects are explicitely taken into account